Traditionally, utility knives have a blade that either (a) is in a fixed, extended position relative to a knife handle but is externally covered by a blade cover or (b) is stored internally in a cover until the blade is manually extended by sliding the blade out of the knife's handle. Some progress has been made to protect users from unprotected blades. For example, more recent utility knifes include blades that retract into a handle or a housing when not in use, or that can be covered by a blade cover or guard. However, such knifes still expose a blade in an unprotected position that can cause accident injury to a user.
The problem of accidental injury has been long recognized, with numerous solutions put forward at various times. U.S. Pat. No. 4,980,977 to Matin et al. titled “Safety Core Cutting Knife” (January 1991), for example, describes a knife having a safety guard that guards a blade when not in use, and automatically retracts as the blade is removed from a work piece. The guard has a manually triggered self-locking release assembly that automatically relocks the guard when retracted. Unfortunately, Matin's locking mechanism is external to the housing. Such a configured can be dangerous because the mechanism can readily jam due to debris. The debris could easily interfere with the assembly's locking or unlocking functions. In addition, Matin's safety guard pivots externally from the housing and off of the blade, rather than being retracted into the housing. Allowing the blade guard to pivot or otherwise move in an exposed manner increases a risk of the guard interfering with the knife's operation, with a target work piece, or with the user.
U.S. Pat. No. 5,878,501 to Owens et al. titled “Utility Knife with Retractable Blade Guard” (March 1999) describes a utility knife having a blade guard where the blade guard can be withdrawn to expose a cutting edge of a blade. Unfortunately, the Owens configuration allows the cutting edge of the blade to remain exposed across multiple cuts or uses.
Still other utility knife designs exist that afford some level of protection. For example, a blade can be coupled to a sliding mechanism disposed within a knife handle. A user can push the sliding mechanism to move the cutting edge of the blade from the handle into an exposed cutting position. The sliding mechanism can also be spring-loaded in a manner that automatically retracts the blade into the handle once a pushing force is removed from the sliding mechanism. Preferred knives should also offer a locking mechanism coupled to the blade or blade guard that prevents accidental extension of the blade.
More recently the present inventor pioneered utility knives having a mechanism that automatically re-locks a protective blade guard. For example, U.S. Pat. No. 7,509,742 to Votolato titled “Safety Cutting Apparatus” (March 2009) discloses a utility knife where a blade guard automatically re-locks into a closed position covering a cutting edge of a blade after a single cut. Another example includes U.S. Pat. No. 7,356,928 to Votolato titled “Utility Knife with Safety Guard Having Reduced Play” (April 2008) where a blade guard retracts into a knife handle and can re-lock into a safety position after use.
Ideally, a utility knife should protect users from a cutting edge of a blade by both a blade guard and a handle of the knife. In such an approach, the blade can be retracted into the knife handle when not in use, and can be extended for a cutting operation. Additionally, a blade guard can protect the user from the extended cutting edge, and can move out of position when the knife is applied to a surface to be cut. It has yet to be appreciated such a utility knife can be manufactured where the knife blade and blade guard pivot relative to each other in a counter reciprocating fashion within a handle of the knife.
Thus, there is still a need for a utility knifes with lockable blade guards.
Unless the context dictates the contrary, all ranges set forth herein should be interpreted as being inclusive of their endpoints and open-ended ranges should be interpreted to include only commercially practical values. Similarly, all lists of values should be considered as inclusive of intermediate values unless the context indicates the contrary.